1. Field of the Invention
Embodiments of the present invention relate to a load port capable of reducing the use amount of gas even when the interior of a wafer transport chamber is set to a special atmosphere, and an EFEM having the same.
2. Description of the Related Art
Conventionally, production of semiconductors has been carried out by various processing steps performed on a wafer. In recent years, circuit miniaturization and high integration of elements have been increasingly promoted. It has been required to maintain a high level of cleanliness around a wafer to prevent adhesion of water and particles to a surface of a wafer. Further, to prevent changes in properties of a surface of a wafer, such as oxidization, it has been performed to make a periphery of a wafer vacuum or nitrogen atmosphere that is an inert gas.
In order to properly maintain such an atmosphere around a wafer, a wafer is managed by placing in a sealable storage pod called a Front-Opening Unified Pod (FOUP), and nitrogen is filled inside the pod. Further, to transfer a wafer between a FOUP and a processing apparatus for processing a wafer, an equipment front end module (EFEM) as disclosed in Japanese Unexamined Patent Application Publication No. 2012-49382 is provided. An EFEM constitutes a wafer transport chamber that is substantially closed inside a housing, comprises a load port that functions as an interface unit between the FOUP on one of opposite walls, and is connected to a load lock chamber that is a part of a processing apparatus on the other of the walls. In a wafer transport chamber, a wafer transport apparatus for transporting a wafer is provided. By using a wafer transport apparatus, a wafer is loaded and unloaded between a load lock chamber and a FOUP connected to a load port.
In other words, a wafer is taken out of the FOUP (a load port) that is one transfer position by using the wafer transport apparatus, and transported to the load lock chamber that is the other transfer position. The processing apparatus performs processing for a wafer transported through the load lock chamber within a processing apparatus called a process chamber. After the processing is completed, the wafer is taken out through the load lock chamber, and returned to the FOUP.
The interior of the processing apparatus is set in a special atmosphere, a vacuum or the like in accordance with the processing, to enable quickly the processing for a wafer. The interior of the wafer transport chamber in the EFEM is kept in a clean air atmosphere at a high level of cleanliness by introducing the air cleaned through a chemical filter or the like, to prevent contamination due to adhesion of particles or the like to the surface of a wafer during transport.
In recent years, as high integration and miniaturization have been advanced more and more, although the cleanliness is relatively high in the wafer transport chamber of EFEM, the influence of the air atmosphere different from the interior of a FOUP or a processing apparatus has been concerned.
In other words, the air atmosphere is likely to permit adhesion of moisture and oxygen to the surface of a wafer, causing corrosion and oxidation. Further, when a corrosive gas or the like used in the processing apparatus remains on the surface of a wafer, it may cause corrosion of a wiring material on the wafer surface and deterioration of yield. Further, a corrosion element accelerates a corrosion reaction, and when both moisture and corrosive gas are present, corrosion may develop faster.
In order to avoid such problems, it is conceivable to set the interior of the wafer transport chamber to a dry nitrogen atmosphere similar to the FOUP. Further, it is also conceivable to set a gas atmosphere by using an appropriate special gas, other than dry nitrogen, depending on the wafer processing contents.
In a conventional EFEM, an internal pressure has been increased to prevent ingress of particles from the outside, and it has scarcely been considered to suppress a gas flow to the outside from a wafer transport chamber and a load port constituting an EFEM. Thus, even if a special gas such as dry nitrogen is supplied to a wafer transport chamber, the gas flows to the outside, and it is difficult to properly maintain and manage the internal atmosphere. A large amount of gas is required, and the cost required for gas increases. Further, if a large amount of gas flows out of the EFEM, depending on the types of gas, the working environment outside the EFEM may be deteriorated.
Embodiments of the present invention have been made to solve efficiently the above problems. In particular, it is an object of the invention to provide a load port and EFEM, which suppress a gas flow to the outside and an air flow from the outside, when a wafer transport chamber constituting an EFEM is set in a special gas atmosphere, thereby reducing the supply amount of gas, and improving the quality of a wafer.